Safari searches in the title bar require tapping "return" twice

This began when I upgraded to El Capitan. Sometimes when I search using the title bar of Safari for a google search, I have to hit the return key twice. A single return will sometimes load search results, but not always.

Deleted com.apple.Safari.plist from my Library folder as part of troubleshooting, but it's still occurring.

I've been having this issue and it's started to drive me nuts. I think I've solved it by altering the search preferences for Safari and disabling most of the 'smart search' options. I've not spent the time going through each to determine which particular option caused the issue. I'm just glad I don't have to keep pressing return twice.

That's a really strange phenomenon. I see two possiblities. Either your return key input isn't being registered because the quick search suggestions are slow when loading, or there's something wrong with your cache.

I would try clearing all website data.

NOTE: You'll have to log into all your accounts again, but this should help clear out the lag, making the browsing experience snappier in general once you're back up and running again.